#!/usr/bin/env python
# -*- coding:utf-8 -*-
# Author:MrNineteen
def sum(n):
    '''
累加
:return: 1+2+3+...+n=
    '''
s = 0
for i in range(1, n+1):
        s += i
    return s


def main():
    print(sum(100))

main()


def sum02(n):
    '''
迭代
:param n: 迭代次數
:return: n+(n-1)+(n-2)+..+2+1= 
    '''
if n == 1
 
:

        return 1
else:

        return n + sum02(n-1)



def main2():
    print(sum02(100))

main()



def sum03(n):
    '''
求和公式
:param n: 第n項
:return: n(n+1)/2=    
    '''
return n * (1 + n) / 2
def  main3():
    print(sum03(100))


main()


# 最簡潔的一行搞定
print(sum(range(1, 101)))